Micropumps have heretofore been proposed for applying light to a gas generating material generating a gas upon exposure to light to allow the gas generating material to generate the gas, and feeding the gas to a microchannel to allow the gas to carry a liquid in the microchannel (see, for example, Patent Documents 1 and 2).
The reason why a gas is generated from a gas generating material is, briefly, that when exposed to light, the gas generating material causes decomposition reaction (a kind of chemical reaction) and thereby generates a gas.    Patent Document 1: Published Japanese Patent Application No. 2005-297102    Patent Document 2: Published Japanese Patent Application No. 2007-279068